Rectifier system



k E nf H. A. WHEELER RECTIFIER SYSTEM Filed April 5, 1941 FIG. I.

April 25, 1944.

' INVENTOR AROLD A. WHEELER V ATTORNEY P'z tented Apr. 25, 19442,347,529 V RECTIFIER SYSTEM Harold A. Wheeler, Great Neck, N.

to Hazeltine aware Y., aaalznor Corporation, a corporation of Del-Application April 5, 1941, Serial No. 386,996 12 Claims. (Cl. 175-363)The present invention relates to rectifying systern and, particularly,to rectifying systems adaptedto separate out, with accurate preservationof wave form, complete half-cycles of an alternating voltage applied tothesystem. While the invention is of general application, it isparticularly suited for use in a system for indicating the wave slope ofsaw-tooth scanning currents commonly used in television systems and willbe described in that connection.

In conventional television systems, the television image is transmittedby the method of transmission of a continuous signal representative ofsuccessive image elements. To reproduce the transmitted image withfidelity, it is essential that the positioning of the multiplicity ofelements in the received image be exactly th same as in the originaltelevised image. To this end, signal-generating and image-reproducingtubes of the cathode-ray type are used respectively at the transmitterand receiver and the cathode-ray beams of the transmitting and receivingtubes are, in general, deflected in synchronism with each other atsubstantially constant velocity, the deflections in both thetransmitting and receiving tubes being in two directions normal to eachother to produce a raster or pattern of parallel scanning lines.Successive incremental portions of each line of the reproduced patternat the receiver correspond to successive elements of the televised imageat the transmitter, whereby the complete pattern of lines together formthe television image at the receiver.

The constant-velocity deflection of the cathoderay beam of thetransmitting and receiving.

cathode-ray tubes is accomplished in one form of television system by adeflecting field produced by a scanning wave of saw-tooth wave form.

Such a wave changes in one sense at a constant rate over a relativelylong trace interval during the formation of one line of the pattern oflines and changes in the opposite sense at a greater rate during arelatively short retrace interval. Since the rate of change of thesaw-tooth wave determines the velocity of deflection of the cathode-raybeam, it is essential that the wave have a constant rate of changeduring the trace interval; that is, that the saw-tooth wave have uniformslope during such interval.

In some cases, a definite departure from uniform slope of the saw-toothscanning wave may be desired to compensate for geometric relations inthe cathode-ray tubes, as to compensate for differences in the degree ofcurvature of the transmitter and receiver cathode-ray tube screens.Thus, it is desirable to be able to indicate visually such wave slope ina simple and effective manner to facilitate the design and adjustment ofthe saw-tooth wave generator. Mere inspection of a reproduced televisionimage is not adequate. Nor is it always adequate merely to reproduce thescanning wave on the screen of an oscilloscope, since slight variationsin the wave slope are not easily detected by visual inspection andespecially is this true 0! the relative magnitudes of such variations.

It has been proposed in accordance with one prior art arrangement thatthe slope of a scanning wave be indicated by inserting a small pickupcoil within the magnetic field oi the deflecting coil to be used withthe cathode-ray tube and then to observe the voltage induced in thepickup coil, which is proportional to the wave slope. Since only theslope during the trace interval is important from the standpoint ofimage reproduction, the relatively large voltage pulse produced duringthe short retrace interval is removed by a clipping or limiting systemand the voltage pulse produced during the trace interval is subsequentlyamplified and reproduced on the screen of an oscilloscope. A linear sawtooth scanning current and resulting magnetic field produce a voltage ofrectangular wave form in the pickup coil. Departures of the reproducedvoltage pulse from a rectangular wave form indicate departure fromlinearity or uniformity of slope oi. the saw-tooth current during-thescanning interval. This indicating system has a disadvantage that theaxis of the original voltage induced in the pickup coil is lost by theaction of the clipping system and it is, therefore, difficult todetermine its correct position. The arrangement consequently is not welladapted for ascertaining exact values of the magnitude of changes ofslope of the scanning wave.

It has been proposed in accordance with another prior art arrangementthat a pickup coil be used as in the arrangement described above andthat the relatively large voltage pulse induced in the-pickup coilduring the retrace interval be removed by the 'use of a rectifier, therelatively smaller voltage pulses induced during the trace intervalbeing subsequently amplified and reproduced on the screen of anoscilloscope. While this arrangement is relatively simple, a rectifierhas inherent capacitive admittance in a direction opposite to that ofits normal conductivity, whereby a portion of the voltage pulse producedduring the retrace interval is coupled intothe pulse amplifier and isreproduced with distortion on the oscilloscope screen. The reproductionof such portion of the voltage pulse of the retrace interval efiectivelyshifts the indication of the axis of the re produced voltage pulses,thereby to introduce in-=. accuracies in measurements made from thereproduced pulse wave form of the magnitude of changes of slope of thesaw-tooth scanning wave.

If a rectifier system is to derive only complete half-cycles of onepolarity of an alternating volt-=' tends to distort the wave form of thevoltage delivered to the rectifier system from the amplifier so that thewave form effectively loses the identity of the equal-area axis of thealternating voltage wave applied to the rectifier system.

It is an object of the present invention, therefore, to provide arectifier system particularly suitable for use in a system foraccurately indieating the slope, and the magnitude of changes thereof,of a saw-tooth scanning wave, over the trace interval, while avoidingone or more of the disadvantages and limitations of the prior artindicating systems of this nature.

It is a further object of the invention to provide a rectifier systemwhich uniformly loads an input circuit connected thereto with uniformconductance over each, complete cycle of an alterhating voltage appliedto the input circuit, whereby the rectifier system presents a uniformresistance to the input circuit for either symmetrical or unsymmetricalwaveforms of alternating voltage applied thereto and retains the waveaxis undisturbed by the rectifying action of the system.

It is an additional object of the invention to provide a rectifiersystem wherein the effect in the rectifier output circuit of theundesired in herent capacitive admittance of rectifier devices includedin the system is greatly reduced, whereby the wave form of the voltagederived by the rectifier system accurately corresponds to completehalf-cycles of one polarity of the alternate ing voltage applied to thesystem.

In accordance with the invention, a rectifier system for derivinghalf-cycles accurately corresponding to half-cycles of an alternatingvoltage applied thereto comprises an input circuit adapted to haveapplied thereto said alternating voltage and rectifier means havingefiective initial conduction potentials which are negligible relative tothe applied voltage and including a pair of rectifier devices coupled tothe input circuit individually to conduct complete half-cycles ofapplied voltage of opposite polarities and having individual resistiveload networks. The devices and their respective load networks have equaleffective values of resistance with respect to the input circuit for therespective half-cycles of applied voltage conducted thereby. An outputcircuit is coupled to the load network of only one of the rectifierdevices for deriving therefrom only complete half-cycles of one polarityof the alternating voltage.

In accordance with a preferred form of the invention, a rectifier systemof the type described comprises a pair of rectifier devices, each havingundesired capacitive admittance in a direction opposite to that of itsnormal conductivity. There is provided means including aunidirectionally conductive device connected in circuit with the loadnetwork to which the output circuit is ecupied for reducing the effectin the output circuit of the undesired gapacitive admittance of therectifier device associated therewith. M

For a better understanding of the present in vention, together withother and further objects thereof, reference is had to the followingdescription taken in connection with the acccmpanying drawing, and itsscope will be pointed out in the appended claims. 0

Referring now to the drawing, Fig. i is a cirs cuit diagram, partlyschematic, of a complete saw-tooth current wave-slope indicating systemembodying the invention; Fig. 2 is a graph ccm= prising curvesrepresenting voltage variations occurring at certain points in theindicating system of Fig. 1 when the canning wavehas uniform slopeduring the scanning interval is used as an aid in explaining theoperation of the invention; and Fig. 3 is a graph comprising curvesrepresenting corresponding voltage vari ations which occur when thescanning wave has nonuniform slope during the scanning interval.

Referring now more particularly to 121g. 1, there is representedschematically a complete indicating system embodying the presentinvention in a preferred form. The system comprises an input circuitincluding a pickup winding Iii adapted to be inserted within themagnetic field of a a rectifier system it embodying the invention anddescribed in more detail hereinafter, the output circuit of which iscoupled to the input circuit of a vacuum-tube amplifier l5. The outputcircuit of amplifier I5 is, in turn, coupled to the deflectingelectrodes it of an oscilloscope H. The oscilloscope l1 additionallyincludes a pair of deflecting electrodes IB normal to the electrodes IEto which there is applied a scanning potential of saw-tooth wave formfrom a scanning generator l9. A synchronizing circuit of the scanninggenerator i9. is coupled by a conductor 20 to the pickunwinding iii,wherebyv the scanning potentials of the generator is are developed insynchronism with the potentials induced in the pickup winding it.

It will be understood that the apparatus just described may, with theexception of the'rectifier system it, be of a conventional constructionand operation, the details of which are well known in the art, renderingdetailed description thereof unnecessary. Considering briefly theoperation of the indicating system as a whole, and neglecting for themoment the operation of the rectifier system It presently to bedescribed, scanning currents of saw-tooth wave form flowing through thewinding 9 from a source, not shown, induce in the pickup winding l0 analternatirig voltage of rectangular pulse Wave form comprisingrelatively large amplitude negative pulses during the retrace intervaland relatively small amplitude positive pulses during the traceintervals. For the purpose of simplifying the description of theoperation, and while the expressions are not strictly accurate since theinducedmulse voltage has an unsymmetrical wave form, the portion of theinduced voltage wave on the positiue side of the equal-area axis willhereinafter be referred to as the positive half-cycles while the portionofthe induced voltage on the negative side of the axis will be referredto as I the "negative half-cycles." Additionally, all references topositive and negative half-cycles will be with reference to thehalf-cycles of the input induced pulse voltage regardless of anyreversal of phase which the induced voltage may undergo at one or morepoints in the system. The pulse voltage induced in winding II is appliedto amplifier l2 and after amplification therein is applied to rectifiersystem H which, removes the large amplitude negative half-cycles toderive in the output circuit of the rectifier system the relatively lowamplitude positive half-cycles representative of the slope of the inputcurrent wave during the trace interval. The positive halfcycles of theamplified pulse voltage are applied to amplifier l5 and, after furtheramplification therein, are applied to the deflecting electrodes IQ ofthe oscilloscope IT to deflect the cathode ray of the oscilloscope I! ina first direction. The cathode ray is deflected in a second directionnormal to the first direction by the deflecting electrodes l6 which areenergized by the scanning potential applied thereto from the scanninggenerator IS, the operation of the latter being synchronized by thepulse voltage induced in pickup winding l0. Consequently, the wave formof the positive half-cycles of voltage induced in the pickup winding IIIis reproduced on the fluorescent screen of oscilloscope l1. reproducedwave at anypoint is a measure of the slope of the saw-tooth current waveat a corresponding point in the cycle.

Referring now more particularly to the portion of the system embodyingthe present invention, the rectifier system H is one for derivinghalf-cycles accurately corresponding to halfcycles of an alternatingvoltage applied thereto. It comprises input circuit terminals 2|, 22 andrectifier means having effective initial conduction potentials which arenegligible relative to the applied voltage and including a pair of likerectifler devices 23, 24 which are coupled to the input circuitindividually to conduct complete halfcycles of the applied voltage ofopposite polarities. The rectifier devices have individual resistiveload networks comprising resistors 25, 26,

- respectively, of equal value but high in relation to the resistancesof the rectifier devices 23, 24 in their respective directions ofconductivity. The sums of the resistances of the rectifier devices 23,24 and their respective load resistors 25, 23 are equal in thedirections of conductivity of the devices, whereby the parallelcombination of the devices and their loadnetworks present to the inputcircuit of the rectifier system l4 substantially uniform resistance forall values of the instantaneous voltage applied to the input circuitfrom amplifier I2, that is, throughout each complete cycle of theapplied alternating voltage and for different amplitudes thereof. Therectifier system includes an output circuit which is coupled to the loadnetwork of only one of the rectifier devices for deriving therefrom onlycomplete half-cycles of one polarity of the alternating voltage. Thiscircuit comprises terminals 21, 26 which are coupled to the loadresistor through a resistor 30 of relatively small value. Each of therectifier devices 23, 24 has inherent undesired capacitive admittance ina direction The value of the opposite to that of its normalconductivity. To reduce the efiect in the output circuit of therectifier system of the undesirable capacitive admittance of rectifierdevice 22, there is provided a unidirectionally-conductive device 29which is coupled with polarity opposite to that of rectifier device 23in shunt to the load resistor 25 through the resistor 30 of relativelysmall value. Similarly, to avoid the effect in the rectifier systeminput circuit of the undesired capacitive admittance of rectifier device24, there is provided a second unidirectionally-conductive device 3|,similar to device 29, which is coupled with polarity opposite to that ofrectifier device 24 across the load resistor 26 through a resistor 32 ofequal value equal to resistor 30. The rectifier devices 23, 24 and theunidirectionally-conductive devices 23 and 3| are all preferably of thethermionic vacuum-tube type with indirectly heated equipotentialcathodes, so that the cathode of each has an initial electron-emissionpotential, the polarity of which is in a direction aiding the normalconductivity of the device. This causes the rectifier devices to have aninitial conduction potential which may be appreciable with relation tothe amplitude of the applied alternating voltage. The electron-emissionpotential and other factors, such as contact potential and space-chargeeffects which are inherent in tubes of this nature, cause the resistanceof such a tube in the direction of its conductivity to vary with thecurrent flowing therethrough and this current, in turn, is dependentupon the instantaneous value of voltage applied to the tube and theresistance of its load network. Thus, the input voltageoutput currentcharacteristic of such tubes is nonlinear over the range of values ofinstantaneous voltage applied to the tube. The efl'ect on the inputcircuit 2 I, 22 of the nonlinear operating characteristic of the devices23, 24, 28, and 3| is substantiallyeliminated by a unidirectional-biaspotential applied across the resistors 30 and 32 from a voltage divider35 across which is connected a source of battery or unidirectionalpotial 33 and which serves to make the effective initial conductionpotentials across the rectifier devices negligible relative to appliedalternating voltage amplitudes of even small values.

The magnitude of the unidirectional potential applied across theresistors 30 and 32 is so proportioned, by adjustment of the voltagedivider 35, with relation to the load networks comprising resistors 25,26 and the operating characteristics of the devices 23, 24, 29, and 3|that the latter devices and the load networks present substantiallyuniform resistance to the input circuit 2|, 22 for both small and largevalues of instantaneous voltage applied to the input circuit.

A portion of the pulse current in the cathode circuit of amplifier I2 isconducted through an adjustable neutralizing condenser 34 to the loadresistor 25, this current having such phase relationship that it iseifective further to reduce in the output circuit of the rectifiersystem the effect of the undesired capacitive admittance of therectifier device 23.

In considering the operation, of the circuit just described, andreferring to Fig. 2, it will be assumed that a scanning current ofsawtooth wave form represented by curve A fiows through the winding 9.This saw-tooth current induces in the pickup winding lo a pulse voltagerepresented by curve B having positive half-cycles a of relatively smallamplitude and negative half -cycles b of relatively large amplitude. Aportion of the voltvelop in the output circuit thereof a pulse voltagerepresented by curve C.

The amplifier pulse voltage C is applied to the input circuit of therectifier system I where it is rectified by the rectifier devices 23 and24 to derive across the load resistors 25 and 28 pulsatingunidirectional voltages corresponding to the original positive andnegative half-cycles, respectively, of the applied voltage. Since theindividual rectifier devices 23 and 24 are effectively coupled without abiasing potential across the input circuit oi the rectifier system itbecause the voltage derived from source 33 is relatively very small, theinitial voltage applied to each of the rectifier devices is in theregion of marginal conduction thereof. By the region of marginal 25conduction is meant the region in which any substantial voltage changeinone sense will render one of the rectifier devices conductive, whereasthe device will not be conductive as a result of a similar change involtage in the other sense. The inherent capacitive admittances of therectifier devices 23 and 24 are compensated by the respectiveunidirectionally-conductive devices 29 and 3! which nearly short-circuitthe respective load resistors 25, 26 insofar as the reverse currentsthrough the respective rectifier devices 23, 24 are concerned. Thus, thewave forms of the voltages derived across the respective load resistors25 and 26 accurately correspond to the wave forms of correspondingcomplete half-cycles of the voltage applied to the rectifier system. Thevoltage derived across the load resistor 25 is represented by curve Dand is applied through the output circuit of the rectifier system to theinput circuit of amplifier I where it is amplified to develop in theoutput circuit of the amplifier a voltage having the wave formrepresented by curve E. The wave form of this voltage is reproduced onthe fluorescent screen of the oscilloscope ii.

The portion of the saw-tooth scanning current corresponding to the traceintervals is represented by the intervals tet1, tz-ta etc., of curve Aof Fig. 2. Since the wave form of the scanning current is assumed to belinear, that is, of uniform slope, during these intervals, the tops ofthe wave reproduced on the screen of the oscilloscope ii are fiat asindicated by curve E. Conversely, the fiat top of the wave form of thevoltage reproduced by the oscilloscope ii] is an indication that thesaw-tooth current has uniform slope during the trace intervals.

if it is assumed that the wave form of the sawtooth scanning currentfiowing through the winch ing ii has non-uniform slope during the traceintervals, as represented by curve F of Fig. 3, curves G, H, I, and J ofFig. 3, respectively, represent the wave form of the voltage induced inpickup winding it, that developed in the output circuit of amplifier 52,that derived from the output circuit of the rectifier system i i, andthat reproduced on the fluorescent screen of the oscilloscope it. Fromcurve J it will be apparent that the saw-tooth scanning current haschanging slope from the beginning to the end of the trace intervals.Since the minimum amplitude of curve J accurately corresponds to theaxis 01' the voltage induced in the pickup winding l0, and representedby curve G, the amplitude of any point, as the a point c, on curve J isa direct measure of the wave slope of the saw-tooth scanning current ata corresponding point to in the scanning cycle. The wave slopes of thescanning current at all points in the trace intervals are thus readilyand acoulo raately determined from the wave form of the voltagereproduced on the screen of the oscilloscope ll.

As previously stated, the unidirectionaily-conductive device 29 nearlyshort-circuits the load 5 resistor 25 with respect to the reversecurrent through rectifier device 23 resulting from its inherentcapacitive admittance. The device 23 has a small internal resistance inits conductive direction so that, were it not for the neutralizingourrent conducted through the condenser 34, a small undesired voltagewould be developed across the load resistor by the negative peaks of thevoltage induced in pickup winding Ill. The neutralizing currentconducted to the load resistor 25 through the neutralizing condenser 34,however, is of the proper phase to oppose that conducted thereto throughthe undesired capacitive admittance of the rectifier device 23 and iseffective to oppose such small undesired voltage, thereby 30 to reducethe cheat of the internal resistance of the device 29 in its conductivedirection and the eflect in the output circuit of the undesiredcapacitive admittance of the rectifier device 23. Thus, the neutralizingcurrent aids the unidirectionallyconductive device 29 in reducing-to aminimum the voltage developed across the load resistor 25 by currentresulting from the inherent capacitive admittance of the rectifierdevice 23. As a result, the minimum amplitude of the pulsating unidiw-rectional voltage developed across the load" resistor 25 accuratelycorresponds to the axis of the pulse voltage induced in pickup windingl0.

Either or both of the unidirectionally-conductive device 29 and theneutralizing circuit comprising the condenser 34 are effective to reducein the rectifier system output circuit the effect of the undesirablecapacitive admittance of the rectifier device 23.

As illustrative of a specific embodiment of the invention, the followinginformation is given for the embodiment of the invention shown in thedrawing:

Frequency of scanning wave cycles From the foregoing description of theinven-- tion, it will be evident that a rectifier system embodying theinvention presents to an amplifier preceding the system the equivalentof a constant high resistance to halfwaves of both polarities oi thealternating voltages in the output of the amplifier. This has theadvantage that it is easy we to develop across this effective highresistance a high vol e and the -:.entconsideredtobethepreierredaccurately corresponding to alternating voltage applied theretocomprising.

amplifier consequently has high gain. Additionally, the netdirectcurrent h the rectifier system thereiore, no tendency to developin the input circuit oi the rectifier system potentialwhich would causethe loss oi the identity oi the equal-area axis oi the alternatingvoltage'applied to the'rectifler systems While there has been describedwhat isat presthis invention, it will be obvious in the art that variouschanges and modificatlons may be made therein'without departing from theinvention, and, it is, thereiore, aimed in the appended claims to coverall such changes and modifications as iall within the true spirit andscope of the invention.

What is claimed is:

1. A rectifier system for deriving l ali-cycles halt-cycles oi an aninput circuit adapted to have applied thereto said alternating voltage,rectifier means having eiiective initial conduction potentials which arenegligible relative to said applied voltage and including a pair 01rectifier devices coupled to said inputcircuit individually to conductcomplete half-cycles of applied alternating voltage applied theretocomprising,-

an input circuit adapted to have applied thereto said alternatingvoltage, rectifier means having eiiective initial conduction potentialswhich are negligiblerelative to said applied voltage and including apair of rectifier devices coupled to said input circuit individually toconduct come voltage oi opposite a,e4v,see I oi said devices havingundesired capacitive ad-i is zero and there is.

mittance in a direction normal conductivity.

opposite to, that of its an output circuit coupled to the load networkoi only one oi said rectifier plete half-cycles oi applied voltage ofopposite polarities and individual resistive load networks for saiddevices, the sums oi the resistances of said devices and theirrespective load networks complete cycle oi said being equal in therespective directions oi conductivity oi said devices, whereby saiddevices and said load networks present to said input circuitsubstantially uniform resistance throughout each complete cycle 'oiwsaidalternating voltage,

work oi only one oi'said rectifier devices for deriving therefrom onlycomplete halt-cycles of one polarity oi said alternating voltage.

3. A rectifier system for networks being equal in the respectivedirections oi conductivity oi said devices, whereby said devices andsaid load networks present to said input circuit substantially uniformresistance throughout each alternating voltage, each one load networkiorto the load network 01 onlyone oi to conduct half-cycles oi devices iorderiving therefrom only complete hali-cyclesoi one polarity of saidalternating voltage, and means connected in circuit with said reducingthe efi'ect in said output circuit oi the undesired capacitiveadmittance oi said one rectifier device during the half-cycles oi theother polari 4. A rectifier system ior CIGXIMhaII-CYOIGS accuratelycorresponding to hali-cycles oi an alternating voltage applied theretocomprising, an input circuit adapted to have applied thereto saidalternating voltage, a pair of rectifier devices coupled to said inputcircuit individually to conduct .hali-cycles oi apphed voltage ofopposite opposite to that oi its an output circuit coupled d rectifierdevices for deriving therefrom 0 complete half-cycles of one polarity oisaid alternating voltage, and means including aunidirectionallyconductive device connected in circuit with said oneload network for reducing the eiiect in said undesired capacitiveadmittance of said one rectifidevice during the halt-cycles of the otherpolarity. i i

5. A rectifier system normal conductivity,

said alternating voltage, a pair or like-rectifier devices coupled tosaid input circuit individually applied voltage oi options ofconductivity of said devices, whereby said that of its normalconductivityan output cir-- circuit 01 the undesireg.

of said devices, whereby load networks present said devices and said tosaid input circuit substantially uniform resistance throughout eachcomplete cycle of said alternating voltage, each ,0! said devices havingundesired capacitive admittance in a direction opposite to that of its Inormal conductivity, an output circuit coupled to the load network ofonly one of said rectifier devices ror deriving thereirom only completehalicycles of one polarity of said alternating voltage, and meansincludin a unidirectionally-conductlve device connected in shunt withsaid one load network ior reducing the effect in said output said onerectifier device.

'7. A rectifier system tor an input circuit adapted to have appliedthereto said alternating voltage, a pair or rectifier devices coupled tosaid input circuit individually to conduct hali cycles of appliedvoltage or opposite polarities and having individual resistive loadnetworks, the sums of the resistances of said devices and theirrespective load networks being equal'in the respective directions ofconductivity alternating voltage, a rectifier device coupled tosaidinput circuit and having a resistive load network, said devicehaving undesired capacitive ad mittance in a direction opposite to thatof its normal conductivity, an output circuit coupled to said loadnetwork for deriving therefrom only complete half-cycles of one polarityoi said alternating voltage, and means including aunidirectionally-conductive device connected in circuit with said loadnetwork for reducing the efiect in said output circuit of theundesiredcapacitive capacitive admittance oi deriving halt-cycles 1 accuratelycorresponding to half-cycles or an alternating voltage applied theretocomprising,

admittance 0! said rectifier device.

'10. A rectifier system for deriving half-cycles 1 accuratelycorresponding to half-cycles of an alternating voltage applied theretocomprising,

an input circuit adapted to have applied thereto said alternatingvoltage, a pair oi rectifier devices coupled to said input circuitindividually to conduct halt-cycles 01 applied voltage of oppositepolarities and having individual resistive load networks, the'sumsoi'the resistances of said devices and their respective load networksbeing of said deviceawhereby said devices and said 4 load networkspresent to said input circuit sub- ,stantially unirorm resistancethroughout each complete cycle oi said alternating voltage, each or saiddevices having undesired capacitive admittance in a direction oppositeto that 01 its normal conductivity, an output circuit coupled to theload network of only one of said rectifier devices ior derivingtherefrom only complete halt-cycles of one polarity of said alternatingvoltage, and means including a pair of unidirectionally-conductivedevices individually connected in circuit with said load networks forreducing the eflect in said input and output circuits rectifier devices.V

8. A rectifier system for deriving half-cycles accurately correspondingto halt-cycles or an alternating voltage applied thereto comprising, aninput circuit adapted to have applied thereto 4o 0! the undesiredcapacitive admittance of said equal in the respective directions ofconductivity of said devices, an output circuit coupled to the loadnetwork of only one of said rectifier devices for; deriving therefromonly complete half cycles of one polarity of said alternating voltage,and a source oi unidirectional potential connected in circuit with saiddevices with a polarity to oppose the conductivity thereoiand having amagnitude-so proportioned with respect to said load networks and theoperating characteristics of said devices that said rectifier devicesand their load networks present substantially uniform resistance to saidinput circuit for all values of instantaneous applied voltage.

11. A'rectifier system ior deriving half-cycles accurately correspondingtoxhalt-cycles' of an alternating voltage applied thereto comprising, aninput circuit adapted to have applied thereto said alternating voltage.a pair of rectifier devices coupled to said input circuit individuallyto conduct halt-cycles of applied ,voltage oi opposite polarities andhaving individual resistive load said alternating voltage, a pair ofrectifier dey vices coupled to said input circuit individually toconduct half-cycles of applied voltage of opposite polarities and havingindividual resistive load networks, the sums devices and theirrespective load networks bein equal in of, said devices, whereby saiddevices and said load networks present to said input circuitsubstantially uniform resistance throughout each or the resistances ofsaid j the respective directions of conductivity complete cycle of saidalternating voltage, each of said devices having undesired capacitiveadmittance in a direction opposite to that oi its normal conductivity,an output circuit coupled to the load network or only one of saidrectifier devices for deriving therefrom only complete halt-cycles ofone polarity of said alternating voltage, and means for conducting tosaid one loadnetwork an alternating current of phase to oppose thatconducted to said one network by the undesired capacitive admittance 0!said one rectifier device tor reducing the eflect in said output circuitof the undesired capacitive admittance of said one rectifier device. I

9. A rectifier system for deriving half-cycles accurately correspondingto half-cycles of an alternating voltage applied thereto comprising, aninput circuit adapted to have applied thereto said networks, the sums ofthe resistances of said devices and their respective load networks beingequal in the respective directions of conductivity of said devices, eachor said devices having undesired capacitive admittance in a directionopposite to that of its normal conductivity, an output circuit coupledto the load network of only once! said rectifier devices for derivingtherefrom only complete half-cycles or one polarity oi said alternatingvoltage, a unidirectionally-conductive device connected in circuit withsaid one load network for reducing the eftect in'said output circuit orthe undesired capacitive admittance of said one rectifier device, and asource oi unidirectional potential connected in circuit with saiddevices with a polarity to oppose the conductivity thereof and having amagnitude so proportioned with respect to said load networks and theoperating characteristics of said devices that said devices and loadnetworks, the sums of the resistances of said devices and theirrespective load networks being equal in the respective directions ofconductivity of said devices, each of said devices having undesiredcapacitive admittance in a direction opposite to that of its normalconductivity, an output circuit coupled to the load network of only oneof said rectifier devices for deriving therefrom only completehalf-cycles of one polarity of said altemating voltage, means includinga pair of unidirectionally -conductive devices individually connected incircuit with said load networks for reducing the efiect in said inputand output circuits of the undesired capacitive admittances of saidrectifier devices, and a source of unidirectional potential connected incircuit with said devices with a polarity to oppose the conductivitythereof and having a magnitude so proportioned with respect to said loadnetworks and the operating characteristics of said devices that saiddevices and said load networks HAROLD A. Warm.

CERTIFICCATE 0F CORRECTION. Patent No. .2, L;7, 529. April 2 19111;.

' mom: A.

It is hereby ceitified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page Lsec- 0nd column, line 9-10, for "eccuraately" z ead "accurately"; line65, for 7-18" read --17-80-; and that the .said Letters Patent should beread with this correction therein that the same may conform to therecord of the case in the Patent Office.

Signed end sealed ch15 11ml day of Novembef, A. D. 19%.

Leslie Frazer s Actingfcommissioner of Patents.

g CERTIFICATE OF CORRECTION. Patpnt No..2,3l .7,529. April 2 19M.

' 7 mm A.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1;,sec-- 0nd column, line 9-10, for "accuraately" read --ac.curatel y; line65, for "17-18" read ----Il .7-8O-;' and that the .said Lgtters. Patentshould be read with this correction threin that the same m conform tothe record of the case in the Patent brricc.

Signed and sealed cm 1mm day of November, A. D. 191m.

Leslie Fr'azer (Sisal) Atingfcommissioner of Patents.

